Party line reverting call by directory number



P. BAKKER `2,602,120

PARTY LINE REVERTING CALL BY DIRECTORY NUMBER July 1, 1,952

ATTORN EY P. BAKKER PARTY LINE REVERTING CALL BY DIRECTORY NUMBER Filed Nov. s, 1948 July l, 1952 2' SHEETS-SHEET 2 PIER BAKKER ATTORNEY Patented `uly 1, 1952 UNITED STATES PATENT oFFlcE PARTY LINE REVERTING CALL BY DIRECTORY NUMBER Pier Bakker, Chicago, Ill., assigner to Automatic Electric Laboratories, Inc., Chicago, Ill., a corporation of Delaware Application November 3, 1948, Serial No. 58,066

8 Claims. 1

The present invention relates in general to automatic telephone system and has for its principal object the provision of a new and improved switching apparatus of the Strowger step-by-step type for use in making reverting calls to automatic subscribers located on thev same party line asV the calling party in response to dialing the directory telephone number of the desired called Party# Heretofore in automatic telephone systems, two methods were utilized in making reverting calls. One method being to provide a special reverting call switch which they calling party, knowing the call was a reverting call and that the desired party was on the same party line, dialed by means of `ajspecal designated reverting call number. The otherJ method does not provide any reverting call 4switch andthe calling party dials the directory number ofthe called party thereby 4utilizing only the regular switch train for extending thek call and ringing the desired party. The present invention is directed to improvements in the latter type in'which reverting calls are made by directory number. o 1

Heretofore in'makingl reverting calls by directory number, the entire switch .train was released and the calling and called parties were feed talking .battery from their individual line circuit. Such' a line circuit, howeverjrequired a threerelay line circuit having aline, aout-olf and a lockout relay, or required special Vmechanism vassociated with the line and cut-off relays of a two-relay line circuit. In the present invention a standard two-relay line circuit is used without interlocking mechanismv and only part of the automatic switch train comprising the finder and selector is released whilethe connector-switch is maintained in `operated position during conversation to feed talking battery to the party` line. Accordingly, one of the features Vof the invention is the provision of an improved Strowgerk stepby-step connector switchwhich is operated in accordance with a portion lof the digits lofV the called subscribers directory number 'to yconnect with the called party line,and which, ifzthe called party is on thesame party-line as the .calling party, is arranged to signal the' called party when the calling party replaceshis'receiver, to cause the release of all the switches in the extended connection except the connector switch, to con- 4lnect a special tone to informl the answering party that the call is a reverting call, andto feed `talk- 1 ing batteryto the party line .during conversation.

eOther objects and features of the invention will be pointed out in the following specification and 2 will best be understood by reference to the accompanying drawings in which Figures 1 and 2 taken together, with Figure 2 to the right of Figure 1, illustrate sufcient details of the automatic telephone system to enable theinvention to be de-4 scribed and understood. v

In Figure 1. the party line comprising subscriber substations A, B, C and D terminates in thev line circuit LC and in the banks ofthe connectors, such as illustrated in detail in Figures 1 vand 2. Finder-selector links, such as F-S, have access to party lines, such as the line illustrated, through the nder portion of the links while the selectors, such as S, have access to connectors, such as the connector illustrated in detail in Figures 1 and 2. The line current LC, the finder F and the selector S are of the well-known type of Strowger switches used in automatic telephone systems and may be similar to the line circuit, finder and selector shown in the Lomax et al. Patent 2,214,908, issued September 17, 1940. The toll selector also shown in Figure 1 is also of the well-known type of Strowger step-by-step switch and is used by the toll operator to vconnect with called subscribers through the illustrated connector switch. y

The connector switch illustrated in Figures 1 and 2 is also of the well-known Strowger type in which the wipers vare raised step-by-step in a vertical direction to select a group of ,lines and then in a rotary stepping motion to select the line of the desired. group. The connector is of the 200 point type having two sets of wipers by means of which the connector has access to 200 lines. A

.minor switch MS is provided in the connector for Y described hereinafter in the detail description.

Ldcal call l' In response to the calling subscriber A removing his receiver a circuit is completed for operating liney relay l0 of LC as follows: ground by way of contacts 22, line conductor l1, through the A substation circuit A, line conductor I6, contacts 2l and winding of line relayv l0 to battery. At contacts H relay l0 grounds conductor |5 to vbusy thisline `to connector switches having access thereto; :atcontact I3 connectsfbattery through acoaieo nder vertical bank (not shown) and starts a search of the rotary line marking as marked through the winding of cut-off relay 20 and -contact I 3. the finder switches through tothe associated selector S and cut-ofi relay 20 is operated. At contacts 2| and 22 the line relay I0 is disconnected When the nder nds the calling line and is restored, at contacts 23 a circuit is'completed from ground (not shown) in the associated link in the usual manner to maintain relay operated independent of contacts I 3. Relay I0, upon restoring,` at contacts ||4 disconnects groundfrom conductor I5 but immediately reconnects groundY through contacts I2 and 23 to maintain the busy marking, Vat contacts I3 opens the original energizing circuit of relay 20 and at contacts I4, disconnects the vertical marking from the finder..

When the iinder switches through to the selector the calling subscriberreceives dial tone in the customary manner and then dials the called subscribers number. The selector S is operated in response tothe rst'digit dialed to operate the selector in a verticaly movement opposite a levelI of Ybank contacts corresponding to thedigit dialed and thereafter automatically rotates the selector wipers in VSearch of an idle connector switch. Assuming that the connector switch, shown in detail inligures l and 2 is the :lirst'y idle connector inthe selected level, then when the wipers 5I to 53 engage the bank contacts 6i to Se the selector S switches through and connects the calling line to the connector. Ground from the selector is extended forward over wiper 53, test conductor S0, vertical offnormal springs VON "|011, and upper winding'of slow-to-release series relay |30 to battery for energizing relay |80. In addition the loop circuit throughthe calling subscribers substation, line circuit LC' and the iinder andl selector link is extended over contacts IIN-|112, NS2-|54, and the lower and upper windings of connector line relay |00 toy battery andV ground toenergize relay |00.

Relay |80 at contacts Iil prepares a point in the iinpulsing circuit to the'vertical magnet VM. Relaygl' at contacts |0| completes an kobvious circuit for energizing slow-'to-release release relay I |01 Relay I I0 at contactsI I2 grounds conductor S0 to hold the selector, the finder and the cut-ofi' relay operated and to busy this connector to other switches having access thereto. At contacts I'I3 relay I I0 completes an obvious circuit for venergizing sloW-to-release hold relay |20. Relay|20 at contacts |22 vgrounds the hold conductor |00 for energizing relay 280 and for later on holding certain other relays in their operated positions and at contacts |23 prepares another point in the pulsing circuit for the VM magnet. The circuit for energizing relay 280 extends from grounded contacts |22, hold conductor. 090, contacts 212 and through the lower winding ofslowto-release relay 280100 battery. 'Relay 280 vper- -faogmsno usefulfunctionat this time.k Y'

, In response to the calling subscriberdialing the second digit" of the called number,line relayIBo .is deenergizied-agnumber of times Acorresponding e to the digit dialed. Each time relay I 00 de-energizes, contacts II open the Acircuit to slow-torelease relay I0 which is maintained in operated condition due toits slow releasing characteristics. The vertical magnet VM is operated once for each de-energization of line relay |00 to step the connector shaft and Wipers in a vertical direction over the following circuiti ground at contacts |02, contacts |23, conductor I'QI, contacts 214, contacts I 84 and winding of Vertical magnet.

A branch of this circuit'extends through the lower winding o1" series relay |80 to hold this relay in operated position during dialing. ln response to the rst vertical step of the'wipers the vertical oiT-normal springs |64 open the circuit through the upper winding of relay |80, the vertical off-normal springs |40 close to prepare a locking circuit for the reverting call relay |40 and the vertical off-normal springs 255 close to prepare a circuit for the connector release magnet RL. Shortly after the last impulse of the second digit, series relay restores and 4atvcontacts |05 prepares the impulsing circuit to the connector rotary magnet RM. j,

The calling subscriber now dials the third digit kof the called number and ythe line relay. |00

follows these dial pulses. The circuit foroperating rotary magnet RM may be traced ...as follows: ground contacts H52,v |23, conductor ISI, contacts 214, |85, 264 and through the winding of rotary rmagnet RM to battery; A branch'of this circuit extends by way of contact 215xthr'ough the winding of slow-to-release rotary series relay 250 to battery. Relay 250 is operated in this circuit and maintains its contacts closed during lthe dialing period due to its'slow releasing'characteristics. At contacts 254 relay'.250completesan obvious short circuit around the windingof relay 210 and at contacts 252c0mpletes the circuit for operating 2 step relay 260 in itsxiirst step. This circuit may be traced as follows: from hold conductor |Y grounded at contacts |22, contacts 252 and 25| and through the. upper winding of 2 'step relay 230' to battery. Two step relay 20|) in operating in itsA iirst step vcloses only the X contacts 252 thereby connecting the grounded hold conductor |90 through the lower winding of relay`26. This short circuits the lower winding of two step relay 260 and vprevents further operation of this relay.

-Shortly after dialing the third digit, slow-torelease relay 250deenergizes and at contacts 252 removes the short circuit from aroundthe lower winding of two step relay 260, whereupon this relaynow energizes'through both its lower and upper windingsl in series to operate its remaining contacts. Atcontacts 264 relay .260 opens the circuit tothe rotary magnet RMv and ,at contacts 255 connects the impulsing circuit to the minor switchrotary magnet MRM.

The calling subscriber now dials the fourth digit to'position the minor switch MS. The line relay-|00 again follows the-transmitted impulses and operates. the minor switclirotary magnet one step for each impulse received. The circuit for operating the minor switch rotary magnet MRM may be traced. as follows: groundcontacts |02, |23, 214, |85, 265 and through the winding of magnet` MRM to battery.V The series relay 250 isv again energized and at contacts 25| removes ground from :the multiplied bank contacts accessible to wiper M2 of the minor switch.V The minori switch rotary ymagnet MRMy rotategs'the wipers MIand M2 one step for each impulse received.` In response to the, first rotaryfstep, of

the .minor switch, the, off-normal springs. 294

and 295 are closed. Contacts l295 prepares ak ,circuit-for relay 210 which relay, however, has its winding short circuited at contacts 254 as long as relay-.250 is operated.-

If .the fourth digit comprises the first set of wipers 2|3, 2I5 and ;2|8 are to be used in .establishing theV connection. In case the fourth digit comprises 6 or more pulses then the second set of wipers 2|4, 2I6 and 2I1are to be used. '.When wiper M2 of the minor switch engages its 6th bank contact, a circuit is completed for operating the wiper switching relay 200 ras follows: ground through minor switch olf -normal contacts 295, the 6th bank contacts engaged'by wiper M2 and through the winding of relay .200 to battery. This circuit is completed as soon. as the Wiper M2 reaches its`sixth bank contact ,and thef wiper switching relay 200.is locked energized over contacts 295 and 206. Wiper switching relay 200, upon energizing, switches from the nor.-

mally connected set of wipers to the normally disconnected set. f :i Shortly after the last pulse of the fourth digit relay 250 restores and at contacts 254 removes the short circuit from around the winding of relay 210. A circuit may now bev traced for operatingA the .slow-,to-operate relay v21|! as follows: ground contacts 295, winding of relay V210 and vthrough theresistance RI to battery., At contacts 212, relay 210 opens the circuitto the slowto-release relay 280 which will restore after an interval.v At contacts 216, relay 210 prepares a release circuit for the minor switch release magnet MRL. f The called lineL is tested before the slow-torelease. relay 280 restores. i In case the line is busyl` a .circuit is completed for operating the busy test relay |30 as follows: from busy ground encountered on the testcontact of the called line,

:either wiper 2|1 or 2I8 and contacts 201 or 208, dependent upon the operated .condition of wiper switch relay 200, and from thence through minor A switch off-normal 294, contacts 285, winding of 5 `pulses or less y 6 at contacts I0 I. opens thecircuitcrelease relay l0 and at contacts |02 connects'groundto-t-he test wiperv v2|1,or 2I8 for a purpose to be de,- scribed later .on in connectionwith reverting calls. f- After.- an intervalslow-to-releaserelease relay I0 restores, and at contacts I I2 disconnects ground from, conductor 60 to release the selector and finder as well as cut-off relay 2,0 in thewell known manner.y At contacts |3 relay I I0 opens the circuit to the slow-to-release hold relay which now releases unless the call just described isa busy relay |30 and through the resistance R to battery. Busy relay |30 energizes over the above traced circuit vand at contacts |3| prepares a circuit for connecting busy tone to the calling subscriber, at contacts |32 prepares a pointinthe circuit for operating the reverting call relay` |40,

at contacts |33 opens a point in the circuit of relay 250 and at contacts |34 prepares a circuit tothe override relay |10, if the toll identiilcation relay |60 is energized or to the reverting. call relay if the c all is a reverting call. -At contacts l |35 relay |30 prepares a circuit for the combined ring .reversing and Ystepping relay 230 which is incomplete at contacts 293, at contacts |36 pre- Ivpares a locking circuit for itself .and at contacts |31 opens the circuit to switching relay 240. Re-

lay 2 8 0 restores after an intervaland at contacts 28| connects the busy tone by way of contacts |64, |3|, 28|, tone condenser TC and contacts 24|ar1d22 to the talk conductors of the connector 'from whence busy tone is transmitted tothe calling subscriber in the well known manner. At

contacts y282 and 283 openspoints in the circuit Vof relay 230, at contacts 284 closes the locking circuit for busy relay |30 which may be traced as follows: from ground contacts 242', |24, |36,

,284 and throughthe winding of relay |30 and re- ;sistanceRto battery. Y When the callingparty hears busy tone and vreplaces his receiver,line relay |00 restores and reverting call.N Relay |20, upon releasing; atccntacts. |22 disconnects ground from -the hold,conductor to, restorethe two step relay 260 and atl-contacts |23 ,opens apoint in theimpulsing circuit.' :At contacts |24, relayv |20 opensk the locking circuitof busy relay |30 whichalso releases and atcontacts |25 closes the release circuits V to the releasemagnets of both theconnectorswitch and theminor Switch ,as follows: .from release ground vconcluctor |28, contacts 25; 244, onelbranch-,extending byway of v219 to theminor switchreleasemagnet MRL to battery and the other branch extending by way ofverticaloiffnormal contacts 255 and through the windingof release magnetv RL to battery.` In response lto the operation of release magnet; B,L, ,the s haf t and lwipers of ythe connector switch are restored toA their normal positions in which.,positions [the vertical oil-normal springs are alsorestoredto open the circuitto release magnet RLc In response tothe yoperation of therelease magnet MRL, the wipers of the minor switch MSare restored to their normal positions and the oinormal contacts 294 and 295 are opened. `In response to the openingen-normal contacts 295 relay 200 restores if operated and relay 210 restores and at contacts 216 opens the circuit to release magnet MRL. Theconnector and minor switch vare fully restored and may be used on subsequent connections. f

Returning now to the time when-the called line was tested for arbusy or an idle condition, it will now be assumed that the line was idle in: stead of busy, and that the test wiper nds rnegative Lbattery instead of .a` ground connection with the result that the busy relay |30 is not operated. Now, when relay 28|)V restores,.relay 280 -atfcon- `tacts- 286 completes ,acircuit for energizing, the

switchingrelay 240as follows: fromground. con.- tacts 242', |24, |31 upper winding 0f switch relay 240, contacts 2'86, 294 and over either ,contacts A201 or 208vto their test wipers 2|1 or 2|.8,A one of scribed holding circuit through its lower winding to 'hold conductor |90. At contacts 243, relay 240 groundsthe test wiper by way of contacts 286 and 294 tomake the called line'busyand "to operate the cut-off relay in the called subscriber line circuit LC. At contacts 244', relay 240 opens the Vrelease circuit extending to the release magnets, at contacts 242 connects a ring-back tone tothe calling subscriber, at contactsV 243 and 244 prepares the ringing circuits as wellfas. completing points in the talking circuits, at contacts 246 connects the ring pick-up lead PU to relay |80. However, if harmonic `ringing is to beA used inings.

tacts to |54 inclusive.

7 steadof codefring'ing, the pick-up lead1-PU is connected to direct ground. At `contacts2||'|, re'- lay 240 prepares a circuit to the `vring reversing relay'230, and at contacts 249 startsfthe ringing machine over conductor RMS in case it is not-already started. Relay |80 is'energized over the pick-up lead PU from directground ifv harmonic ringing is used, or over U4the pick-upfleadPU when such lead isgrounded Sat the start fof the ringing. code cycle in the *code-ringing machine inthe usual manner. The circuit for energizing relay |80 extends over contacts |82, 246 and 229 through the rupper winding of-frelay |30 to battery.L At contacts |83 relay |80 closes a locking circuit for itself through ground'and resistance R2 afterv disconnecting the pick-up'lead PU at contacts |82,` and at contacts |81 completes vthe ringing-A circuit. In case party lines are Yto be code rung then coded generator from the selected generator lead, lterminating in the/minor 1 switch bankv accessible to wiper Mi is sentto the called line. In case the party lines are to be selectively signalled by diierent frequencies,` or

byharmonic ringing, theny wiper MI selects the desired frequency lead. In' either casethe ringing circuit may be traced from the selected gen'- erator` lead, Gl Vto G5, bank contacts engaged by wiper M|,`contacts and `|8|, through the upper Winding ofv ring cut-off relay 220, contacts 233 (if theringreverse relay is unoper'ated)V contacts 224,Y 244, contacts 203 or 204, wipers -2|5 or 2|6, over the called subscribers substation circuit and ringer to ground for divided ringing, or back over wipers 2|3 or 2N, contacts 20| or 202, contacts 243, 223 and 23|v to ground for bridged ringing. Incase ring reverser relay 230 is operated then generator is applied in the reverse manner over contacts 232 and back to grounded contacts 23'4'. The ring reverse relay 200 is operatedl over wiper M2 .andy contacts 241 from grounded con'- ductor |80 in case the ringing digit for operating the minor :switch is iivefor less.

Y When the calledparty answers ring cut-off relay 220 operates over the above traced Yringing circuit.l AtY contacts'226,relay220 completes a locking circuittogrounded holdfcondu'ctorlil .throughits lower Winding, lat contacts 22291 opens there circuit torelay 80 which releasesafter'an intervaLat contactsl223 and 2.24 disconnectsithe ringing circuit and` at contacts 222 and;.225com -pl'etes the talking circuit to the back bridg'evre.-

The circuit for energizing back bridgeA layV |50. relay` maybe traced as follows:vr from ground lower .Windingoi relay |50, contactslli, 225, 244,

203, Wiper `2|5'over the talking conductors of the purposes.' fRelay |50 feeds talking battery to the called line and relay |00 feeds talking battery'to Thetalking circuitinclude's the the calling line. Y f 1 heavy talking conductors as shown on the draw- After conversation and'Y in response to the called party hanging up, back bridge relay |50 deenergizes and reverses battery back to normal at con- At'contacts |50, relay |50 connects ground from c`ontacts122|^to supervisory lead- SUPY-I ior. indicatingwhen the call is held by the `calling party. At contactsf 8 I-,;relay1| 50 opens one of `thecircui'ts maintaining the hold relay. |20v inr energized. position. 'Whe'n'- the callingp'arty replaceshisreceiver', lineV relay |00 restores and` at contacts ||l|iv opens the-:circuit to'slow-to-release relay |0... After an interval release relay ||0 restores and at contacts `|'I2 disconnects ground.` from conductorI 60 to thereby causey therelease ofithe selector SL and finder .F'andthe 'fout-orf. relay 20 inthe well known manner. Atcontactsl I3', relay ||l1 opens theroircuit'to-.relay |20 which restores after an interval.. Relay.|20`,. uponA releasing, at contacts '122. disconnects .ground from hold conductor 00 to release-the ring cut-off relay 220, `two step relay. .200iandvswitching. relay 240.. At contacts E43/,relay 240 disconnects ground from the' test wiperto remove therbusy. condition from the called line and at contacts 244 completes the previously traced .circuits for the' connector releaseimagnet' RLand vthe` minor switch release magnet. MRL. These release magnets restore the connector andl minory switches to normal in the same .manner aspreViOuSly described. When the connector and minor switches are restored; their cul-normal contacts open to restore relaysr 200 and 210. In .case the calling party releases first, linere lay |00 restores followed 'by relay |I0, and in this casea circuit may bei completedV .from contacts |02, |23, 2173, :|33, and ||5'to the supervisorylead SUPYJ for indicating to the attendant that this switch is held.. by lthe called4 party. The `connector switch is maintained busy'from grounded contacts 253, 245 and |l|` until the called subscriber replaces hisireceiver. lWhenV the' called party hangs up, back bridge relay |50'1deenergizes and at contactsl 55 opens the circuit to hold relay. |20'. After..` an interval', relayv 120i restores and opens circuits tov relays 260, 240 and 220 as previously described.k The release of: switching relay 240 again completes: theicircuit to the release .-magnets` ofl the .connector .and minor switches to restore theseswitches to their normal positions. y

PBX 'hunting In case the directory number of ya'group of private branchV rexchange (PBX) trunks ijs called 'and theyrst trunk in this groupv is busy, Ythe 'switch-hunts fora-n idle trunkV in this group. `On calls to theV PBX; trunk groups the normalv post 'springs' NP, FiguretZ, areoperated on a specic connector level in response Ato the vvertical` operatonrcfthe connector switch to prepare a circuit "contacts 25| completes the circuit for operating YthelPBlirelayfilil 0l as follows :V from. grounded hold conductor |90, contacts 25|, iifth bank contacts engaged by wiper, M2, operated normal posit contacts 296 and' 4through the 'winding of relays-290 to battery. A similarcircuit may also =be` traced for relay' 290 including the'tenth bankcontacts and wiper M2 in case the last digitdialedwasf. In `dialing the last digit 0 the Wiper M2 momentarily restson its sixth: bank contacts to complete lground fthrough a`00` ohm'resistance.

the previously traced circuit for wiper switching relay 200 which operates and' locks.

' If the PBX trunk line, upon which the'connector wipers are resting, is busy, the connector test wiper will be grounded-with the result that busy relay |30 is energized over 'the previously tracedcirc'uit before relay 280 restores. At contacts |35, busy relay |30 completes acircuit from the test wiper to relay 230 as follows: from grounded test'wiper 2|8, contacts 208, 294, 293, 283,y |35, 231, 289 and 282 and through the lower winding of relay 230`to battery. In this instance, the ring reverse'relay 230 is to be used as a stepping relay for automatic rotationy of uthe wipers.-` At contacts 236, relay 230 completes a locking circuit for itself from groundedI hold conductor |90, contacts 236, 289 and 282 through its `lower winding. At contacts 235, relay 230 completes the circuitfor maintaining relay 280 in operated position, from ground, contacts 222', 248, 235, 263 and through the upper winding of relay 280 to battery. Rotary magnet RM is also operated in the following `circuit to step the connector wipers an'additional rotary step; ground, contacts 222{, 248, 235 and' through winding of rotary magnet RM vto battery. Near the end of its stroke, rotary magnet RM opens contacts 289 to open the circuit to relay l23|) which thereupon restores. At contacts 235, re-

lay 230 opens the' circuitsto the rotary magnet and relay 280 with the result that the rotary magnet'RMrestores to close contacts 289. "The wipers-have r'now been operated into,l engagement with th'terminals of vthe next PBXtrunk and if the second trunk is busy ground potential on the test contact thereof holdsthe busy relay; in operated position with the result that relay 230 is again operated to again cause the connector wipers to take another step. When an idle PBX trunkv is found, busy relay |30 releases and after an interval," slowto-relea'serelay '280 likewise releases. `When relay 280 restores the switching relay `240 is operated in the same manner as previouslyv described 4-to switch to this idle PBX'line.A 'If'all ofthe PBX! trunks are busy, thewipers ofi-the connector will step to4 thelast Contactin the group where'the test wiper will encounter a Relay 230 isrnarginal with respect'to this Vground connection through the 500 ohm resistance and `will not operate."y BusyA relayV |30, however, remains operated through this 5 00 ohm resistance and ground tojsend the busy signalback to the callingsubscriber. Y

*PBX hunting in the second 100 group takes place in the same manner as just described exceptzjthat` digit"0,vins te ad of the digit ,5, is dialedi-"xnthis case-the wiper'switching relay 200'2is`-"dperatedv and locked during'r the' momentary closure of its circuit in positionsixl of the minorfswitch. lThe Y operation' of Yrelay 200 switches"y wiper setsto permit PBX hunting in the second 100 group, the operation is the same asipreviouslydescribed except that wiper 2 |1 is used instead oftest wiper 2|8.

:when an. idle une' isafound/busy remy 13u" restores, relay 280frestores'and relay 240 operates. :Relay |30 at contact'sfl31prepares a point in thecircui'tiof switching relay 240 and .relay 280 at contacts 286 completes the circuit for operating switching relay 240 as follows: ground contacts 242', contacts |24, |31, upper winding-of switching frelay 240, contacts 286, 294; 201, connector test wiper 2 |1 and over the test conductor the call`through I l0 of the called PBX line through the Winding of the PBX cut-off relay to battery. After oper-` ation of the switching relay 240, the switch operates'in thev same manner as previously described. for a local call. This PBX operation is substantially the same as that disclosed in my copending application Ser. No. 770,085, led August 22, 1947, now Patent No. 2,542,272, granted February 20, 1951.

Night service to these PBX lines are provided by dialing either digit 1 or 6, as the last digit on the minor switch dependentupon the 100 group desired. In this case the PBX relay 290 is not operated and therefore `the contacts 293 are'not closed to yprovide automatic rotation with the result that if the particularcalled night line is busy, then busy tone willbe transmitted back to the calling party.

Toll call f An incoming toll callr from an operators-position comes in over the toll selector TOLL SE- LECTOR Figure l, andsuch'selector'seizes the connector illustrated if idle. In'response to this seizure ground is fed forward from rthe toll selector over lead Cf, conductor 60,V VON |64 and through the upper winding of re1ay=|80"to battery Vto energize this relay to prepare the circuit to the vertical magnet-VM. A loop circuit is closed acrossA conductors?- and '.N'for. operating line relay- |00'and toll relay11|60 in series.V This circuit :rnay be traced vvas follows: ground upper which is grounded as a result "of the operation of relays |00, ||0 vand |20. 'At contacts |62 relay |60 prepares a point in th'ecircuit for twostep override relay |10. The operation of line relay |00 causes the operations of relays ||0 and |20 as previously described. VRelay |20 at contacts |2| closes a short-circuit around the upper winding of toll relay but this relay remains operated over its lower' winding.'` Relay |60 at contacts prepares a .circuit forftran'smitting flash busy to the toll operatorinstead'of busy tone if the called local line isbusy.

The toll operator may now dial the'remainingY digits of called subscribers number. whereupon relay |00 follows the dial pulses to operate the connector in the same manner as previously described.

If the ca lledline'.4 is busy relay |30 is 4operated in the same manner as previously described and when'relay 280 releases 'flash ,busyisnnected back to the operator"throughcntacts |65, |3|, 28| and over the EC: lead tothe -toll switch train. The toll Operator may release the connection A if desired ormay cutfin on the busycalled line to'verify the busy condition. Inv order to cut in on the busy called line, the toll operator now dials the digit 1 to cause the restoration and reenergization of line relay |00. Relay |00, in restoring, completes the following circuit 'for operating two-step override relay |10in its first step: ground vcontacts |02, |23, 214, |34, M6162, |16 and upper winding of. relay |10 to'b'attery. In itsfirststep relay.. |10 closes only its Xeontacts |11 thereby closing a short circuit varound. itslower windngfrom ground at Vcontacts 242".

When the line relay reenergizes after the single'v over the heavy talking lconductors vand wipers to the called line to notify thecall'ed partyA that a reverting call is bein'g'madel* f -f Depending upon the'type of 'ringingemployed,y the calling partymay or may not hear the called party being rung. If the ringing cani-be' heard; the calling party will answer after itfcea'ses,j and if it cannot be heard, the calling party will answer after a sufficient length of time'has passed.- After'the callingpa'rt'y answers tov complete `the call, talking battery isrfurnished to both parties from the-windingsof rrelay I 50,',H l' Y If the called partyffa'il'sto answer, ringingwill continue until the? calling partyA answers,v When the calling party answers ring cut-oli' frelay'-2`20 isoperated as before 'to open the ringing ci `uit` andto operate relay |50. n "-'f f After conversation and in responseto fbothfthe callingand called parties hanging upftheirzreceivers relay l50 resto'res. At contacts 155 relay 50 opens ythe circuit to'hold Vrelay 120 which restores after'an intervalV to disconnect ground from holdcon'duct'or I`90- tof release relays-"21,202 240 and 260. A* At 'contacts |25', relay "|120 fcompletes the previously traced circuits for operating the release magnets RL and MRL to restore the switches tonorlnal;` `Off-normal contacts M9 open when the connector shaft and wipers'are restored to release reverting call relay |40 and off normal contacts 295 release relay 210 and relay 200 if operated. The connector is now'f'ully restored and may be used on subsequentcallls. v

From the foregoing it will therefor beseen that I have provided a connector switchwhich is operated in accordance withthe telephone directory numberk of the called party line subscriber in making reverting calls, whicr'i`-"permitsv the 're- "lease of all preceding switches except the connector when the calling party hangs up and which connector is held in operated position durlng conversation to feed talking battery to both the calling and called parties, and then released after conversation when both parties hang up their receivers.

What is claimed is:

1. In a telephone system, party lines, a plurality of stations on each party line, a connector switch having access to said lines, means controlled by a calling station on one of said lines for directively operating said connector switch to connect with said one line and to selectively signal any selected one of said plurality of stations on said one line in making a reverting call, a revertingcall tone relay included in said connector switch, said reverting call tone relay having a vibrating reed which alternately charges a condenser and then discharges said condenser over said one line, means actuating said tone relay in response to said selected station answering to discharge said condenser over said line to signal the called subscriber that a reverting call y has been answered.

. 2. In a telephone system, a party line having calling and called terminals, a connector switch having access to said called terminals, 'other switches operated by a calling station on said line for extending a connection fromrthe calling terminals of said line to said connector switch, means for operating said connector switch to select the called terminals of said line, means for transmitting a busy tone to the calling station in case the called station ison the same line-as the calling station, means responsive to the calling station replacing his receiver for releasing said other switches to vdisconnect said other switches from said line, for v`operatingsa'ld connector switch toseize said selected called l:terminals of said line'and to automatically signal said called station on said'line,"me`ans in -said connector switch for feedingtalkingbatteryover saidI called' terminals on' a reverting "call, a revertin'g call tone relay included in said connector switch, said reverting vcall tone jrelay havin'ga vibrating reed which alternately charges acondenser "and gthen discharges said condenser Vover said one-linefxneans actuating said tonerelay in response to said'v selected station answering to discharge"'said condenser over said line to signal the 'called Vsubscriber that a reverting call'has been'answeredxl l 3. In a telephone-system; a partyfline, a' plurality Yof party line substations connected to 'said party line, acontrol line and a control relay associated with saidV party'lin'e, each party substation lhaving `a different vtelephone directory numberas'sig'ned thereto, ai switch train'including atleast one selectorfswit'ch'and aconnector switch operated iii-responseto the calling party dialing the directory numberof a "called party to prepare "a connection to the called line ofi'the called'party,v means -for transmitting la busy-'tone kto th'ecalling party'in case the calling'partyis on the? same Iline asthe called party; means ein saidfc'onnector f' switch 'for `selectively signalling the calledparty', means responsive to the: calling party replacing .his 'receiver after hearing the busy tone for releasing part of said switch train including said selector switch; means including said `control relay responsive to aisignal transmitted over said control line associated `withsaid calledline fo'r maintainingsaid 'connector switch, for completing'.=the prepared connection to said called hline from: said rconnector switch .and 'for operating said signalling means for selectively signalling the called party; and means in said connector switch for feeding talking battery to both the calling and called parties when they answer.

4. In a telephone system, party lines, a control relay and a control line associated with each of said lines, a switch train including a iinderselector link and a connector for 'extending calls to and from said lines, means responsive to the initiation of a call from a calling line for oper,- ating said finder to connect withv saidv calling line, calling subscriber controlled means for operating said selector to connect with said connector, for thereafter directively operating said connector to a called one of said lines and for selecting the signalling current to be applied to said called line in accordance with the directory telephone number of the called party; means in said connector responsive to the calling party replacing his receiver in case the called party is on the same line as the calling subscriber; means including said control relay operated responsive to a signal transmitted over the control line 4associated with said calling line, upon operation of said last means, for releasing said finder and selector, means in said connector also operated upon the calling party replacing his receiver for maintaining said connector operated, for completing the connection with said called line, and for selectively signalling the called party in accordance with said "selected signalling current, and means in said connector for feeding talking battery during conversation to both the calling and called parties on a reverting call.

5. In a telephone system, a party line; a connector switch having access to said line and having a busy relay for transmittinga busy -tone to |`the calling sta-tion, a revertingcall yrelay for use -in controlling said connector switchto complete reverting calls betweenstations onfsaid line. and a vholdrrelay for maintaining said connector switch in operated position; means for operating said busy relay in response vto va calling station onv said `line operating said connector' switch to connect with said line in making Va revertingvcall tofanother station on said line, a circuit controlled by said 'busy relay and completed inresponse to said calling station hanging up his re-f ceiver for genergizingsaid 'reverting call relay in series with said hold relay, and means controlled by the energization of said reverting call relay for-short circuiting said busy relay V'to cause its release. I

6. In a telephone system as claimedin claim '5 including circuit meanseffective after operation of Vsaid reverting call relay for maintainingsaid reverting call relay and saidrholdt-relay,energized independent of "said circuit and Vindependent of thefoperative condition-of said .busy relay. t

7. .Infa'telephone-system, a party line having afplurality ofstations, a connector. switch having access to said line to complete calls thereto, a

hold relay in said switch operated in response toV the seizure, of said switch onva call for 'maintaining said switch in operated position, a 'reverting call relay in saidswitch operated in response to one of saidfst'ations on said line calling another station onrsaid line .for controlling saidswitch tocomplete a reverting callvncluding both said calling and called stations on said line, relay means and a circuit energized by said relay means for energizing saidreve'rting call relay'and said hold relay .in series, and a second lvcircuit for maintaining said reverting call'relay 'and said hold relay energized independent of said relay means and said rst mentioned circuit.

8. In a telephone system, a partyvline; Aa connector switch having access tov said line and having a busy relay for transmittinga busy vtone to the calling station, a reverting call relay for use in controlling said connector switch to -com plete reverting calls between stations on said line,

-mentioned seriescircuit during the signalling vjovf thelcalled station, said second circuit opened and'f a third circuit closed in response to I4'said called station. answering for maintaining lsaid holdf-relay in operated position. l I f x Y y PIER BAKKER.

REFERENCES CITED iny the The following references are Yof record file of thispatent: l A' UNITED STATES PATENTS l Number Name vDate 1,329,287 Campbell -Jan. 27, 1920 1,755,378 Willis Apr. 22, 1930 1,910,972 Stokely May-23, 193,3 2,187,186 Wallace Jan. 16, 1940 2,335,473r

Bakker Nov. 30, 1943 

